/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/MeshSelectionFunctions.h
Grow or Shrink the Selection on the TargetMesh to connected neighbours. For Vertex selections, Expand includes vertices in one-ring of selected vertices, and Contract removes any vertices with a one-ring neighbour that is not selected For Triangle selections, Add/Remove Triangles connected to selected Triangles For PolyGroup selections, Add/Remove PolyGroups connected to selected PolyGroups
static [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * ExpandContractMeshSelection ( [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * TargetMesh, [FGeometryScriptMeshSelection](API\Plugins\GeometryScriptingCore\GeometryScript\FGeometryScriptMeshSelection) Selection, [FGeometryScriptMeshSelection](API\Plugins\GeometryScriptingCore\GeometryScript\FGeometryScriptMeshSelection) & NewSelection, int32 Iterations, bool bContract, bool bOnlyExpandToFaceNeighbours )